This invention relates to the delivery of yarn from wound yarn packages on a creel. The invention is of particular, but not exclusive, interest in relation to the delivery of a warp sheet directly to a fabric-producing machine, especially of a tire cord warp sheet to a loom for weaving tire reinforcement fabric.
Creels are known in which the yarns are drawn through the creel to a front guide stand having with a large number of thread guides, and thence to a fabric-producing machine. One such creel is a fixed position creel to which the yarn packages are brought, for example in skips, buggies or on pallets, for re-loading. When it is required to replace the yarn packages on the fixed creel, the creel is re-loaded in situ. The yarn from each yarn package is knotted to the retained end of the respective previous yarn drawn from the creel, adjacent the yarn package or at the front of the creel. This loading operation takes considerable time. During this time, the fabric-producing machine may be shut down. Alternatively, it may be fed with yarn from an adjoining creel, two creels being located upstream of the fabric-producing machine. This is not space-efficient. Furthermore, it will be appreciated that the yarn packages undergo considerable handling between their winding on and their placement on the creel. They must be transported from the winding machine to the creel, and moreover there must generally be two stages to the transportation because it is the practice to leave a newly wound yarn package for a period of time between winding and use, to allow the yarn time to "relax".
Tire cord yarn packages have heretofore generally been flanged bobbins with a yarn weight of 2 to 3 Kg. However, these are proving of inadequate size, in view of the faster weaving and knitting machines which are now available. For example, if a loom can operate at a speed three to four times greater than a traditional loom, as is now proving possible, the bobbins are unwound in a third to a quarter of the previous unwinding time. Once unwound, the creel must be reloaded. Overall productivity has not therefore increased as much as the greatly superior performance of modern looms and warp knitting machines should allow.
One approach might be to simply scale up from the system described above, and use much larger flanged bobbins. In the context of tire cord yarn packages, a yarn weight of about 10 to 12 Kg would be suitable. However this necessitates very heavy and costly winding machines and a very large investment in flanged bobbins.
Flangeless, cross-wound yarn packages, for example produced by means of the modern Cabler twisting machine, would be preferred. Production of such yarn packages, commonly known as "cheeses", would be more economical than production of very large yarn packages using flanged bobbins. Flangeless, cross-wound yarn packages have the further advantage that they may be wound onto cheap tubular cores, for example of cardboard.
However, flangeless cross-wound yarn packages are much more delicate than yarn packages wound onto flanged bobbins, since they have no end constraints. Therefor they must be handled more carefully and is it desirable to minimise handling operations.
A further type of creel which has been employed, and through which yarn has been drawn towards a fabric-producing producing machine, is the trolley creel, which is made up of a number of independently movable trolleys, which can be loaded directly from the winding machine, and moved into place as part of the creel when required. The trolley creel therefore offers the advantage over the fixed creel that yarn package handling is minimised. No intermediate double handling is necessary. Thus, it is more desirable, from the point of view of handling, to use a trolley creel for cross-wound yarn packages, than a fixed creel. It might be thought, therefore, that the problems of delivering yarn efficiently to a modern fast fabric-producing machine could be solved by using large cross-wound supply packages on scaled-up trolley creels. However, it takes longer to assemble and thread up a trolley creel than it does to re-load and thread up a fixed creel. When the empty set of trolleys is taken away to the winding area for re-loading, all that remains is the fixed front set of yarn guides immediately upstream of the fabric-producing machine. Thus when the new set of trolleys is brought into position, all yarns from each trolley must be threaded forward to the fixed front guide stand for knotting in. The loom stop time is in fact that required to cut the previous array of yarns at each joint between trolleys, remove the empty trolleys, install a new full set of trolleys, to thread all the yarns through the creel forward to the guide stand behind the loom, which can be a time-consuming operation, and finally to knot in and pull the knots through. The loom stop time is considerably longer than for the fixed creel, mainly because of the threading-through operation; and the larger the creel, the more time consuming is the threading-through operation.